The radius of curvature of the curved surface of a plano-convex lens is 20 cm. If the refractive index of the material of the lens be 1.5, it will a) act as a convex lens only for the objects that lie on its curved side b) act as a concave lens only for the objects that lie on its curved side c) act as a convex lens irrespective of the side on which the object lies d) act as a concave lens irrespective of the side on which the object lies
Correct option is C) Given, R=20cm,μ=1.5=23 Then, R1=0,R2=−20cm f1=(μ−1)[R11+R21]=(1.5−1)[0+201]⇒f=40cm Thus it behaves as a convex lens.
